1. Field of the Invention
The present invention relates to an embedded magnetic component transformer device, and in particular to an embedded magnetic component transformer devices with reduced coupling and improved isolation properties.
2. Description of the Related Art
It is known, for example, in US 2011/0108317 A1, to provide low profile transformers and inductors in which the magnetic components are embedded in a cavity in a resin substrate, and the necessary input and output electrical connections for the transformer or inductor are formed on the substrate surface. A printed circuit board (PCB) for a power supply device can then be formed by adding layers of solder resist and copper plating to the top and/or bottom surfaces of the substrate. The necessary electronic components for the device may then be surface mounted on the PCB.
Compared to conventional transformers, an embedded design allows a significantly thinner and more compact device to be built. This is desirable because typically the space available for mounting the transformer device onto a PCB, for example, a motherboard of an electronics device, will be very limited. A transformer component with a smaller footprint will therefore enable more components to be mounted onto the PCB, or enable the overall size of the PCB and therefore the entire device to be reduced.
In transformer design, it is desirable to optimize the energy transfer between the primary and the secondary transformer windings. Typical factors that may degrade or impede efficient energy transfer include the resistance of the windings themselves, sometimes called ‘copper loss’, and poor coupling of the magnetic field between the primary and the secondary sides.
In order to mitigate the first of these factors, known transformer design often use leads to connect to the windings that are as short as possible, thereby reducing their associated electrical resistance. Short leads or connections are, however, relatively difficult to produce and are therefore labor intensive. This results in increased costs of production and occasionally reduced reliability for the finished device.
To address the coupling problem, the primary and secondary windings may be placed very close to one another. In alternative designs, the primary and secondary windings may be interleaved. However, while placing the primary and secondary windings close to one another aids with coupling, there remains a conflicting need to electrically isolate the primary winding from the secondary winding. In isolated transformer designs, a high isolation level is usually achieved by physically separating the primary and secondary windings from one another. Without significant physical separation, isolation can be achieved by using insulation materials. For wound transformers, for example, triple insulated wire may be used. For an embedded transformer designs, isolation may be improved by using conformal coatings or core covers to insulate the ferrite magnetic core. Windings may also be insulated with insulating tape, or may be separated by increasing the size of the transformer or by using multi-layer PCBs, thereby putting different windings on different layers. However, all of these techniques increase size and add cost to the production process.
Thus, there is a need for an embedded magnetic component transformer design, capable of being downsized, while preserving isolation and optimizing energy transfer.